System and Operating Modes of the S7-400H
5-4
Automation System S7-400H Fault-tolerant Systems
A5E00068197-07
Self-Test
Malfunctions have to be detected, isolated and reported as quickly as possible.
Consequently, wide-ranging self-test functions have been implemented in the
S7-400H that run automatically and entirely in the background.
The following components and functions are tested:
• interconnection of the central controllers
• processor
• Memory
• I/O bus
If the self-test detects an error, the fault-tolerant system tries to eliminate it or to
suppress its effects.
5.2 System Modes of the S7-400H
The system modes of the S7-400H result from the operating modes of the two
CPUs. The term “system mode” is used to obtain a simplified expression which
identifies the concurrent operating modes of the two CPUs.
Example: Instead of “the master CPU is at RUN and the standby CPU is in the
LINK-UP mode” we use “the S7-400H is in the Link-Up system mode”.
Overview of the system modes
The following table shows the system modes that are possible with the S7-400H.
Table 5-1 Overview of the S7-400H system modes
System Modes of the
Operating Modes of the Two CPUs
Master Standby
Stop STOP STOP, deenergized, DEFECTIVE
Startup STARTUP STOP, deenergized,
DEFECTIVE, no synchronization
Single Mode RUN STOP, TROUBLESHOOTING,
deenergized, DEFECTIVE, no
synchronization
Linking RUN STARTUP, LINK-UP
Update RUN UPDATE
Redundant mode RUN RUN
Hold HOLD STOP, deenergized, DEFECTIVE
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